Lung ultrasound (LUS) and Lung ultrasound Scores (LUSS)
Bedside LUS exams were acquired during the neonatal hospitalization by one doctor over 5-year experience on LUS. Pacifier or sedation could be used in some neonates if uncooperative. Images were collected by a portable ultrasound system (Mindray M9) with a high-frequency (L12-4S,4-12MHz), linear-array probe. The neonates were placed in a supine, prone or side position during the exams.
We divided each lung into 6 regions and labelled them, by using the anterior axillary line, posterior axillary line and the line connecting the nipples (Fig. 1). The most pathological pattern acquired in each intercostal space during an entire respiratory cycle was retained for the further analysis and considered representative of the area score. The longitudinal scan was done first, to correctly identify the pleura; a clip at least as long as one respiratory cycle was stored for offline analysis. The transversal scan was obtained by a rotation centered on the pleura, until complete disappearance of the ribs; a second clip was stored. Both longitudinal and transversal sections were collected on the anterior, lateral, and posterior chest wall.
e utilized semi-quantitative LUSS, grading between 0 and 3, depending on the severity of aeration loss in each lung region (Table 1). The following images were recorded2 and scored: presence of A-lines, maximum number of B-lines, visual percentage of lung area occupied by confluent B-lines, visual pleural involvement >50% or ≤50%, and tissue-like patterns (consolidations).
LUSS was independently assessed by two experienced ultrasonic doctors for inter-observer reproducibility. Intra-observer analysis was performed by using the recorded images 4 weeks after the initial reading was conducted.